Irwin was struck while filming a sequence for his 8-year-old daughter Bindi's new TV series.

He was pulled unconscious on board his research boat, Croc One, for a 30-minute dash to the Low Isles, where an emergency helicopter had been summoned about 11am.

Crew performed CPR during the voyage, but medical staff pronounced Irwin dead about noon.

Those with him say he was swimming in shallow water, snorkelling, as his cameraman filmed large bull rays.

"He came over the top of a stingray and the stingray's barb went up and went into his chest and put a hole into his heart," said his friend and manager, John Stainton.

Mr Stainton said bad weather had stopped filming for their documentary Ocean's Deadliest, about some of the world's most dangerous sea creatures.

Irwin decided to shoot some film for Bindi's series.

"He said, 'I might just go off and shoot some segments for Bindi's show, just stuff on the reef and little animals'," Mr Stainton said.

"The next thing I heard on the radio was there was a medical emergency, the little dinghy he was in was bringing him back with the crew."

Within hours, Irwin's death was headline news in Australia and on CNN International, Sky and BBC World.

A larger-than-life character famous for his enthusiasm for wildlife and his catchcry exclamation "Crikey!", Irwin and his American-born wife, Terri, had two children, Bindi and Robert Clarence, 3, known as Bob.

Terri Irwin, who often appeared on TV with her husband, was told of his death while trekking near Cradle Mountain, a holiday area in Tasmania. She returned to Queensland last night.

Irwin drew international condemnation in 2004 when he held Bob, then a baby, while feeding a giant crocodile at Australia Zoo, the wildlife park he owned on Queensland's Sunshine Coast. But he was unrepentant.

"What I would do differently is I would make sure there were no cameras around," he said.

Irwin's television programme, The Crocodile Hunter, started in 1992 and gained huge popularity around the world on the cable network Animal Planet.

He was filmed dodging the strike of deadly taipan snakes, sticking his head down animal burrows or standing chest-deep in crocodile-infested swamps.

While his antics won him a following in countries such as the US and Japan, some Australians regarded him as an over-the-top parody of the ocker Aussie male and a national embarrassment.

But in February, Tourism Australia presented him with an award for his contribution to tourism.

Australian wildlife film producer David Ireland said the stingray barb would have been as deadly as a bayonet.

A marine biologist, Associate Professor Ross Coleman, said it was rare for a stingray to kill an adult human.

"You hear of people getting injured by standing on them ... but they rarely die," said Professor Coleman, from Sydney University's Institute of Marine Science.

Irwin also drew fire when he used his celebrity status to campaign against a plan for limited hunting of saltwater crocodiles in the Northern Territory.

The scheme was supported by the territory's government, cattle ranchers and Aborigines, but was dropped after Irwin lobbied federal Environment Minister Ian Campbell.

Born in Victoria, Irwin developed his passion for wildlife when his father opened a small reptile park on the Sunshine Coast. Irwin took over the park in 1991 and turned it into the multimillion-dollar Australia Zoo business.

New Zealand man remembers ray's 'phenomenal power'

News of Irwin's death brought back a flood of memories for Havelock North man Mark Holder, who survived a nasty attack in January.

Mr Holder was pierced in the upper groin by a stingray's barb at Tangoio beach, in Hawkes Bay.

The barb went in more than 10cm, narrowly missing arteries and tendons. "The barb went in and came straight out again ... it all happened very quickly and most of the damage was done when the barb came out because of the serrated edges," he said.

Mr Holder, 47, suffered blood poisoning from the attack.

"The power of the stingray was phenomenal. It lifted my torso out of the water ... I thought I'd been punched."

Mr Holder said he heard of Irwin's death from a work colleague.

"I can certainly see how [a stingray] could kill you. I feel sad that such a colourful character has died."

Kelly Tarlton's aquarium curator and marine biologist Andrew Christie said stingrays were common around New Zealand waters, but he wasn't aware of any deaths in New Zealand.

"People get stung by them quite often here ... but most injuries are lower leg injuries in shallow waters."

Kelly Tarlton's "Stingray Splash" encounter, where members of the public "get up and close and personal" with stingrays, had strict safety measures in place.